Washing machine

ABSTRACT

A washing machine, more particularly, an improvement in the structure of a drive unit included in a drum type washing machine is disclosed. The washing machine includes a tub for receiving wash water therein, a drum rotatably disposed in the tub and adapted to wash laundry received therein, a shaft penetrated through the tub to thereby be connected to the drum, the shaft being adapted to transmit a drive force of a motor to the drum, a stator coupled fixedly to a rear wall portion of the tub, and a rotor including at least one magnet, a back yoke defining a magnetic path, and a rotor frame rotatably disposed at the outside of the stator, the rotor frame being connected to the shaft so as to transmit a rotating force of the rotor to the shaft. The rotor frame includes a side wall portion and a rear wall portion, and is made of an aluminum material.

This application claims the benefit of the Korean Patent ApplicationNos. 10-2005-0111504, 10-2005-0111505, 10-2005-0111506 and10-2005-0111507 filed on Nov. 21, 2005 which are hereby incorporated byreference as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a washing machine, and moreparticularly, to an improvement in the structure of a drive unitincluded in a drum type washing machine.

2. Discussion of the Related Art

Generally, drum type washing machines are designed to perform a washingoperation by use of a frictional force between a drum and laundry as thedrum is rotated by a drive force of a motor transmitted thereto in astate wherein the laundry is received in the drum together with washwater and detergent. The above described washing operation manner hasseveral effects of causing damage to laundry as little as possible whilepreventing entangling of laundry and also providing excellent washingeffects by pounding and rubbing.

Now, the configuration of a conventional drum type washing machine willbe described in brief with reference to FIG. 1.

Referring to FIG. 1 illustrating the configuration of the conventionaldrum type washing machine in longitudinal sectional view, theconventional washing machine comprises a tub 2 installed in a cabinet 1and a drum 3 rotatably installed in the center of the tub 2.

The tub 2 is mounted, at a lower side thereof, with a motor 5 a and inturn, the motor 5 a is connected to a motor pulley 18 by means of ashaft.

The drum 3 is mounted, at a rear side thereof, with a drum shaft, and adrum pulley 19 is mounted on the drum shaft.

The drum pulley 19 mounted on the drum shaft and the motor pulley 18connected to the motor 5 a are connected to each other by means of abelt 20 as a power transmission element.

The cabinet 1 is provided, at a front side thereof, with a door 21, anda gasket 22 is provided between the door 21 and the tub 2.

A hanging spring 23 is mounted between an inner ceiling surface of thecabinet 1 and an outer upper surface of the tub 2 and adapted to supportthe tub 2. Also, a friction damper 24 is mounted between an inner bottomsurface of the cabinet 1 and an outer lower surface of the tub 2 andadapted to alleviate vibration of the tub 2 caused during a dehydratingoperation.

In the above described conventional washing machine, a drive force ofthe motor 5 a is transmitted to the drum 3 by way of the motor pulley18, the drum pulley 19, and the belt 20 connecting the motor pulley 18and the drum pulley 19 to each other. Such an indirect powertransmission manner, however, has the following problems.

Firstly, since the drive force of the motor 5 a is transmitted to thedrum 3 through the belt 20 wound on both the motor pulley 18 and thedrum pulley 19 rather than being directly transmitted to the drum 3,there is a high potential loss of energy in the transmission course ofthe drive force.

Secondly, in the course of transmitting the drive force of the motor 5 ato the drum 3 through the above described several elements, such as themotor pulley 18, the drum pulley 19, and the belt 20, and the like,there inevitably exists a problem of severe noise as compared to thecase where the drive force is directly transmitted to the drum 3.

Thirdly, a necessity for a great number of elements for transmitting thedrive force of the motor 5 a to the drum 3, such as the motor pulley 18,the drum pulley 19, the belt 20, and the like, consequently, causes acomplicated product assembling operation.

Fourthly, the above described great number of elements for transmittingthe drive force of the motor 5 a to the drum 3 may result in aproportional increase in the number of potential failure areas, and thishas a problem of increasing the generation frequency of failures.

In conclusion, due to the above described power transmission manner inwhich the drive force of the motor 5 a is indirectly transmitted to thedrum 3 only by way of the motor pulley 18, the belt 20, and the drumpulley 19, the conventional drum type washing machine has problems of ahigh potentiality of failures and noise generation as well as excessiveconsumption of energy and seriously, may result in deterioration inwashing performance thereof, etc.

To solve the above described problems, the applicant of the presentinvention has proposed to use a direct connection type motor in a driveunit of a drum type washing machine, as disclosed in Korean PatentLaid-open Publication No. 10-2001-0037607.

In the above published patent invention, there is provided a rotorframe, which is formed by pressing an iron plate and installed totransmit a rotating force of a rotor to a drum directly while performingitself the function of a back yoke having a magnetic path. It could befound that the disclosed rotor frame has a capability of solving theabove described problems of the indirect power transmission manner whileachieving a simplified structure.

However, forming the rotor frame by pressing the iron plate has adifficulty, due to characteristics of a press operation, to obtain arequired accuracy, more particularly, concentricity, when the thicknessof the iron plate exceeds a predetermined value. On the other hand, whenthe rotor frame is formed by use of an iron plate having a thicknessless than the predetermined value, there is a problem in that the rotorframe cannot obtain a required strength and may fluctuate duringrotation.

Furthermore, to provide a passage of magnetic flux, that is to say, amagnetic path for the flow of magnetic flux generated by electriccurrent flowing through coils of a stator, it is essential to provide aback yoke, which is made of a magnetic material and has an appropriatethickness, behind a magnet. Here, it is noted that the thinner thethickness of the back yoke, the lower a saturation point of the magneticflux. Accordingly, when the rotor frame serving as the back yoke has asmall thickness, there is a limit to increase the output of a motor evenif the amount of current is increased to obtain a strong output.

Consequently, the attempt to form the rotor frame having the function ofthe back yoke by use of the iron plate in views of diversification ofproducts reaches a limit due to the above described thickness problem ofthe rotor frame.

Also, due to characteristics of the iron plate, there is a risk in thatthe rotor frame tends to gather rust on its surface easily. The rust maycause deterioration in the strength of the rotor frame and in the worstcase, there is a risk in that rust powder that falls from the rotorframe is attached in an air gap between the magnet and the stator,thereby acting to restrict rotation of the rotor.

In addition, the rotor frame, made of the iron plate, has a difficultyin the implementation of any subsequent process for improving accuracyand other processes.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a washing machine thatsubstantially obviates one or more problems due to limitations anddisadvantages of the related art.

An object of the present invention is to provide a drum type washingmachine in which a drive unit, more particularly, a rotor frame that isadapted to transmit a rotating force of a rotor to a shaft directly, hasan improved structure suitable to transmit a drive force of a motor to adrum directly, thereby achieving the effects of reducing the generationpotential of noise and failure as well as excessive consumption ofenergy and of increasing the durability and stability of the washingmachine.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, awashing machine comprising: a tub for receiving wash water therein; adrum rotatably disposed in the tub and adapted to wash laundry receivedtherein; a shaft penetrated through the tub to thereby be connected tothe drum, the shaft being adapted to transmit a drive force of a motorto the drum; a stator coupled fixedly to a rear wall portion of the tub;and a rotor including at least one magnet, a back yoke defining amagnetic path, and a rotor frame rotatably disposed at the outside ofthe stator, the rotor frame being connected to the shaft so as totransmit a rotating force of the rotor to the shaft, wherein the rotorframe comprises a side wall portion and a rear wall portion, and is madeof an aluminum material.

The coupling structure between the tub and the stator may be altered invarious manners and thus, the detailed configuration and method foraccomplishing the above coupling structure also may be altered invarious manners.

Preferably, the rotor frame is formed by die casting, and the side wallportion and the rear wall portion of the rotor frame are integrallyformed with each other.

The rear wall portion of the rotor frame may be provided, at a centerposition thereof, with a connector, which is serration-coupled onto anouter circumference of the shaft and adapted to transmit the rotatingforce of the rotor to the shaft. Here, the connector may be made of aninsulating material and integrally formed with the rotor frame by insertmolding.

The washing machine may further comprise: a bearing housing providedbetween the rear wall portion of the tub and the stator and coupledfixedly to both the tub and the stator, the bearing housing receiving atleast one bearing therein to rotatably support the shaft. Preferably,the bearing housing is made of a metallic material.

Preferably, the side wall portion of the rotor frame is extended forwardfrom an edge of the rear wall portion, and the side wall portion of therotor frame is formed, in a circumferential direction thereof, with aledge having a seating plane for supporting the magnet thereon. Withthis configuration, the magnet can be more stably secured to the rotorframe.

Preferably, the stator comprises: a stator core including at least onewinding portion around which a coil is wound and an annular body portiondefining the magnetic path; and an insulator for insulating the statorcore from the coil. The stator may have thirty six poles, and the rotormay have forty eight poles.

The back yoke may be attached to an inner surface of the side wallportion of the rotor frame in a circumferential direction by use of anadhesive, and the magnet may be attached to an inner surface of the backyoke in a circumferential direction by use of an adhesive. The back yokeis made of a magnetic material to define the magnetic path. Here, theback yoke may be fabricated to have an optical thickness in views of theperformance of the motor.

The above described drum type washing machine according to the presentinvention has the following effects.

Firstly, the washing machine of the present invention has a directconnection motor and thus, has the effect of significantly reducing thegeneration of noise and failure as well as the loss of power. Also, withthe use of the metallic bearing housing, the washing machine of thepresent invention is applicable to products having a high-temperaturedrying function, without the risk of thermal deformation.

Secondly, in the washing machine of the present invention, the rotorframe is made of an aluminum material and thus, has no risk of gatheringrust thereon. This results in an increase in the durability of themotor.

Thirdly, the rotor frame of the present invention has a magnet seatingplane for achieving a highly efficient mounting operation of the magnet.Also, with the provision of vent holes having the function of moisturedischarge and ventilation, it is possible to prevent overheating of themotor while protecting the motor from invasion of moisture. Thisconsequently has the effect of increasing the reliability of the motorand extending the lifespan of the motor.

Fourthly, according to the present invention, the rotor frame is formedby die casting an aluminum material. Accordingly, the rotor frame can bemanufactured with a simplified manner while guaranteeing an improvedprocessability required for any subsequent process. Also, forming therotor frame by use of a light-weight material is efficient to minimizethe power loss of the motor due to the inertia force of the rotor frame.

Fifthly, the aluminum rotor frame provides a flexibility to ensurefreely change in the thickness of the back yoke in views ofdiversification of products. This enables an increase in the overallthickness of the rotor frame and consequently, the rotor frame is freefrom unwanted fluctuation during rotation thereof, thus resulting inreduced noise and vibration. In addition, the change possibility of thethickness is advantageously applicable for the sake of reinforcing thestrength of the rotor frame.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a longitudinal sectional view illustrating the configurationof a drive unit included in a conventional drum type washing machine;

FIG. 2 is a longitudinal sectional view illustrating important parts ofa drum type washing machine according to a first embodiment of thepresent invention;

FIG. 3 is a right side view of FIG. 2, in which the illustration of amotor is omitted;

FIG. 4 is a partially cut-away perspective view illustrating a rotorshown in FIG. 2;

FIG. 5 is a perspective view illustrating a stator shown in FIG. 2;

FIG. 6 is a perspective view illustrating a connector shown in FIG. 2;

FIG. 7 is a bottom perspective view of FIG. 6;

FIG. 8 is a longitudinal sectional view schematically illustrating theconfiguration of a drum type washing machine using a direct connectionmotor according to a second embodiment of the present invention;

FIG. 9 is an enlarged longitudinal section view of the portion “A” ofFIG. 8, illustrating the configuration of a drive unit included in thedrum type washing machine according to the second embodiment of thepresent invention;

FIG. 10 is a partially cut-away perspective view illustrating theconfiguration of a rear wall portion of a tub shown in FIG. 9;

FIG. 11 is a perspective view illustrating a bearing housing shown inFIG. 9;

FIG. 12 is a bottom perspective view of FIG. 11;

FIG. 13 is a sectional view taken along the line I-I of FIG. 11;

FIG. 14 is a longitudinal sectional view illustrating the configurationof a drum type washing machine using a direct connection motor accordingto a third embodiment of the present invention; and

FIG. 15 is a longitudinal sectional view illustrating the configurationof a drum type washing machine using a direct connection motor accordingto a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

In the present invention, a motor, more particularly, a stator iscoupled fixedly to a rear wall portion of a tub. A method for couplingthe stator to the tub may be changed according to respective preferredembodiments of the present invention.

Now, a first embodiment of the present invention will be described indetail with reference to FIGS. 2 to 7.

FIG. 2 is a longitudinal sectional view illustrating important parts ofa drum type washing machine according to a first embodiment of thepresent invention, and FIG. 3 is a right side view of FIG. 2, in whichthe illustration of a motor is omitted.

FIG. 4 is a partially cut-away perspective view illustrating a rotorshown in FIG. 2, FIG. 5 is a perspective view illustrating a statorshown in FIG. 2, FIG. 6 is a perspective view illustrating a connectorshown in FIG. 2, and FIG. 7 is a bottom perspective view of FIG. 6.

The drum type washing machine according to the present embodimentcomprises a tub 2 installed in a cabinet (not shown) and used to receivewash water therein, a drum 3 rotatably provided in the tub 2 and adaptedto wash laundry received therein as it is rotated, a shaft 4 penetratedthrough the tub 2 and connected to the drum 3, the shaft 4 being adaptedto transmit a drive force of a motor 5 to the drum 3, and a stator 14having winding portions around which coils are wound, the stator 14being coupled fixedly to a rear wall portion of the tub 2.

In the present embodiment, the washing machine further comprises a rotor13, which includes magnets 13 c, a back yoke 300 having a magnetic path,and a rotor frame rotatably disposed around the stator 14. Here, therotor frame is connected to the shaft 4, to transmit a rotating force ofthe rotor 13 to the shaft 4.

The rotor frame has a side wall portion 13 b and a rear wall portion 13a, and is made of an aluminum material.

In the present embodiment, the washing machine may further comprise afront bearing 6 a and a rear bearing 6 b installed, respectively, on anouter circumference of either end of the shaft 4, and a bearing housing7 provided on a rear wall surface 200 of the tub 2 for supporting thefront and rear bearings 6 a and 6 b.

In the present embodiment, a connector 16 may be provided in such amanner that it is serration-coupled onto an outer circumference of theshaft 4, in particular, at a position behind the rear bearing 6 b andalso, coupled to the rotor 13, thereby serving to transmit the rotatingforce of the rotor 13 to the shaft 4.

Here, the bearing housing 7 is provided between the rear wall surface200 of the tub 2 and the stator 4 so that it is coupled fixedly to boththe tub 2 and the stator 4. Also, the bearing housing 7 is adapted torotatably support the shaft 4 by means of the front bearing 6 a and therear bearing 6 b.

In this case, the bearing housing 7 is made of a metallic material,preferably, made of an aluminum alloy. Also, preferably, the connector16 is made of an insulating material and integrally formed with therotor frame via insert molding.

The metallic bearing housing 7 is integrally formed, at a center portionthereof, with a hub 700. The front and rear bearings 6 a and 6 b arelocated in the hub 700. Around the hub 700 are formed a plurality ofcoupling bosses 701 in such a manner that the coupling bosses 701 arespaced apart from another by a regular distance in a circumferentialdirection of the hub 700. The coupling bosses 701 are used to secure thestator 14 to the bearing housing 7 by use of coupling members 15 d. Theabove described configuration of the bearing housing 7 is clearly shownin FIG. 3.

The hub 700, which is located at the center portion of the metallicbearing housing 7, is formed, at different positions of an innercircumference thereof, with short-stepped portions 8 a and 8 b. Theshort-stepped portions 8 a and 8 b serve to support the front and rearbearings 6 a and 6 b, respectively, so as to prevent the respectivebearings 6 a and 6 b from being separated from the bearing housing 7.

Of the short-stepped portions 8 a and 8 b formed along the innercircumference of the bearing housing 7, the short-stepped portion 8 a,which is formed at a front position, has an “L”-shaped form suitable tosupport a rear end of the front bearing 6 a that is installed on theouter circumference of a front end of the shaft 4. On the other hand,the short-stepped portion 8 b, which is formed at a rear position, hasan “L”-shaped form suitable to support a front end of the rear bearing 6b that is installed on the outer circumference of a rear end of theshaft 4.

The shaft 4, which is located in the bearing housing 7 and adapted totransmit the drive force of the motor 5 to the drum 3, is formed, atfront and rear locations on the outer circumference thereof, withpositioning short-stepped portions 9 a and 9 b for determining theinstallation positions of the front and rear bearings 6 a and 6 b on theshaft 4.

The front end of the shaft 4 is coupled to a spider 10 that is providedat a rear wall portion of the drum 3. Also, to prevent the shaft 4 fromgathering rust thereon, a brass bushing 11 is press fitted around aportion of the shaft 4 extended between the spider 10 and the frontbearing 6 a. Here, the bushing 11 is provided, around an outercircumference thereof, with a sealing member 12 for preventingpermeation of moisture into the bearings 6 a and 6 b.

The rotor 13, which constitutes a part of a direct connection motor 5,is coaxially coupled to the rear end of the shaft 4. The stator 14 islocated inside the rotor 13 so as to constitute the direct connectionmotor 5 along with the rotor 13. Here, the stator 14 is coupled fixedlyto the coupling bosses 701 of the bearing housing 7. Of course, it willbe appreciated that the coupling bosses 701 may be formed at the stator14.

The rotor 13 includes the aluminum rotor frame.

As shown in FIG. 4, preferably, the rotor frame has the side wallportion 13 b and the rear wall portion 13 a, which are integrally formedwith each other, and is formed by die casting an aluminum material.

Specifically, the side wall portion 13 b of the rotor frame is extendedforward from an edge of the rear wall portion 13 a in a directionperpendicular to the rear wall portion 13 a. The side wall portion 13 bis formed, in a circumferential direction thereof, with a ledge having aseating plane 130 for supporting the magnets 13 c that are attached toan inner surface of the side wall portion 13 b in a front portion of theinner surface. The rear wall portion 13 a of the rotor frame iscentrally formed with a hub 132. Here, the hub 132 is coupled to theconnector 16, to allow the rotating force of the rotor 13 to betransmitted to the shaft 4 through the connector 16.

Around the hub 132 of the rotor frame are radially formed a plurality ofcooling fins 133. The cooling fins 133 serve to blow air toward thestator 14 during rotation of the rotor 13, so as to remove heatgenerated in the stator 14. In this case, each of the cooling fins 133is formed to have a predetermined length in a radial direction of therotor frame.

Preferably, the cooling fins 133 are integrally formed with the rotorframe and extend radially from the hub 132 to the ledge to have a heightdifference between the hub 132 and the ledge. On the basis of the heightdifference, the cooling fins 133 can be linearly formed or curvedconvexly or concavely. With this configuration, the cooling fins 133 canact to blow air concentratively to specific portions of the stator 14having the highest cooling requirement.

Although FIG. 4 illustrates the cooling fins 133 that are configured tohave the highest height at the side of the hub 132, it will beappreciated that, conversely, the cooling fins 133 have the highestheight at the side of the ledge.

In the present invention, the rear wall portion 13 a of the rotor framehas a plurality of vent holes 134 perforated between the respectiveadjacent cooling fins 133. The vent holes 134 have the roles of moisturedischarge and ventilation.

With the provision of the cooling fins 133 and the hub 132, the rotorframe of the present invention can achieve a reinforced rigidity of therear wall portion 13 b. Also, the cooling fins 133 and the hub 132 canbe formed simultaneously via a single fabrication process and therefore,achieve a reduction in manufacturing costs.

The hub 132 of the rotor 13 has a center through-hole 131, a pluralityof coupling holes 137 equidistantly formed around the centerthrough-hole 131, and a plurality of positioning holes 138 equidistantlyformed around the center through-hole 131 between the respectiveadjacent coupling holes 137. The coupling holes 137 are used to couplethe connector 16 to the rotor 13. Here, the connector 16 isserration-coupled onto the outer circumference of the rear end of theshaft 4 at a position behind the rear bearing 6 b. The positioning holes138 are used to determine the assembling position of the connector 16.Here, a coupling member 15 a is coupled into the shaft 4 by passingthrough the through-hole 131. With the use of the coupling member 15 a,there is no risk in that the shaft 4 is unintentionally separated fromthe connector 16.

The connector 16 is made of a resin material having a differentvibration mode from that of the aluminum rotor 13. Preferably, theconnector 16 is made of an insulating material and integrally formedwith the rotor frame via insert molding.

The connector 16, as shown in FIGS. 2, 6, and 7, has coupling holes 162perforated in an edge region thereof along a circumferential direction,to correspond to the coupling holes 137 formed in the hub 132 of therotor 13. The connector 16 also has positioning protrusions 160integrally formed at positions between the respective adjacent couplingholes 162. As the positioning protrusions 160 are inserted into thepositioning holes 138 of the rotor 13, the coupling holes 137 of therotor 13 are automatically aligned with the coupling holes 162 of theconnector 16.

In addition, the connector 16 has a center hub 163, a serration 164formed at an inner circumference of the hub 163 to be engaged with aserration 400 formed on the rear end of the shaft 4, and reinforcingribs 161 formed at an outer circumference of the hub 163 for reinforcingthe strength of the hub 163.

As shown in FIGS. 2 and 5, the stator 14, which constitutes the motor 5along with the rotor 13, includes a ring-shaped insulator 140, and coils142 wound on winding portions 141 arranged at the outside of theinsulator 140. In addition, coupling ribs 143 are integrally formed withthe insulator 140 inside the insulator 140, to secure the stator 14 tothe bearing housing 7.

The stator further includes a stator core, which consists of the windingportions 141 around which the coils 142 are wound, and an annular bodyportion having a magnetic path. The insulator 140 serves to insulate thestator core and the coils 142 from each other.

The stator core may be an annular spiral core having a multilayeredstructure, which is obtained by spirally winding an iron plate,consisting of the winding portions 141 and the body portion, from thelowermost layer to the uppermost layer.

Alternatively, the stator core may take the form of an annular sectionalcore, which is obtained by coupling a plurality of arched stator coresections, each consisting of a plurality of arched stator core piecesstacked one above another in multiple layers, with one another.

A tub bracket 17 is coupled onto an outer circumference of the tub 2 andadapted to secure the bearing housing 7 at the rear side of the tub 2.In this case, a method for coupling the tub bracket 17 to the tub 2 maybe changed according to the material of the tub 2. For example, if thetub 2 is made of stainless steel, preferably, tub bracket 17 may becoupled to the tub 2 by welding.

Here, the tub bracket 17 has extensions, which are extended rearwardbeyond the rear wall surface 200 of the tub 2. Each extension of the tubbracket 17 is perforated with a coupling hole 170 so that an associatedone of the coupling members 15 d is penetrated through the coupling hole170, to thereby be coupled into an associated coupling recess 702 of thebearing housing 7.

The bearing housing 7 has a plurality of extensions radially extendedfrom the center thereof. As the extensions are coupled to the tubbracket 17, the bearing housing 7 is secured to the tub 2. If thebearing housing 7 has three extensions, it can be called “trivet type”.

The bearing housing 7 has a self-aligning rib 703 formed in acircumferential direction thereof at the outside of the coupling bosses701, the self-aligning rib 703 having a ramp 703 a at a side thereof. Tocorrespond to the self-aligning rib 703, the insulator 140 of the stator14, which is coupled to the coupling bosses 701 of the bearing housing7, has a self-aligning rib 144 formed at an inner circumference thereofin a circumferential direction. Similarly, the self-aligning rib 144 hasa ramp 144 a at a side thereof, so as to be engaged with the ramp 703 aof the self-aligning rib 703 of the bearing housing 7.

Now, the operation of the drive unit having the above describedconfiguration, which is included in the drum type washing machineaccording to the first embodiment of the present invention, will bedescribed.

If the rotor 13 is rotated as electric current is sequentially appliedto the respective coils 142 of the stator 14 under the control of amotor driving controller (not shown) attached to a control panel, theshaft 4, which is serration-coupled to the connector 16 coupled to therotor 13, is rotated. Thereby, power is transmitted to the drum 3through the shaft 4, thus enabling rotation of the drum 3.

Meanwhile, in the present embodiment, preferably, the stator 14 hasthirty six poles and the rotor has forty eight poles. The greater thenumber of the poles, the easier the positional detection and control ofthe stator and the rotor can be accomplished.

Here, the forty eight poles of the rotor alternately define a north poleand a south pole in such a manner that twelve permanent magnets, eachhaving a total of four poles, are coupled inside the rotor frame. Thepermanent magnets may be coupled by use of an adhesive.

Of course, the back yoke also may be coupled inside the rotor frame byuse of an adhesive. Here, the back yoke has to be made of a magneticmaterial because it must have a magnetic path.

Hereinafter, the assembling procedure and effects of the drive unitincluded in the drum type washing machine according to the firstembodiment of the present invention will be described.

First, the bearing housing 7 of the present invention is coupled to thetub bracket 17 by use of the coupling members 15 d as the couplingmembers 15 d are penetrated through the coupling holes 170 of the tubbracket 17. Here, the tub bracket 17 was previously welded to the outercircumference of the tub 2. Thereby, the bearing housing 7 is secured tothe rear side of the tub 2.

That is to say, in a state wherein the tub bracket 17 is welded fixedlyto the outer circumference of the tub 2, the bearing housing 7 iscoupled to the tub bracket 17 to thereby be mounted onto the rear sideof the tub 2.

The assembled bearing housing 7 is made of a metallic material, such asan aluminum alloy and the like, and therefore, has no thermaldeformation even under a high temperature condition. Accordingly, thebearing housing 7 is applicable to a drum type washing machine having ahigh-temperature drying cycle.

In the present invention, the bearing housing 7 is formed, at the frontand rear positions of the inner circumference thereof, with the“L”-shaped short-stepped portions 8 a and 8 b. Accordingly, once thefront and rear bearings 6 a and 6 b are mounted on the outercircumference of both the ends of the shaft 4, the rear end of the frontbearing 6 a and the front end of the rear bearing 6 b can be supportedby the short-stepped portions 8 a and 8 b, respectively.

That is to say, the metallic bearing housing 7 is able to support boththe bearings 6 a and 6 b without the risk of unintentional separation byuse of the short-stepped portions 8 a and 8 b formed at oppositepositions of the inner circumference thereof.

Also, the shaft 4, which is located inside the bearing housing 7 andadapted to transmit the drive force of the motor 5 to the drum 3, isformed, at the front and rear locations on the outer circumferencethereof, with the positioning short-stepped portions 9 a and 9 b,whereby the assembling positions of the front bearing 6 a and the rearbearing 6 b on the shaft 4 can be easily determined.

As described above, the front end of the shaft 4 is coupled to thespider 10 that is provided at the rear wall portion of the drum 3, andthe brass bushing 11 is forcibly press fitted around the portion of theshaft 4 between the spider 10 and the front bearing 6 a to prevent theshaft 4 from gathering rust thereon.

Also, the sealing member 12 is installed around the outer circumferenceof the bushing 11 to prevent invasion of moisture into the bearings 6 aand 6 b.

Meanwhile, the bearing housing 7 has the coupling bosses 701equidistantly formed in a circumference thereof at the outside of thehub 700. Thereby, as the coupling members 15 d, having penetratedthrough the stator 14, are coupled to the coupling bosses 701, thestator 14 can be strongly secured to the bearing housing 7.

Here, since the rotor frame is formed by die casting an aluminummaterial, it can be fabricated with a simplified process without therisk of rust. In addition, the rotor frame has a light weight due tocharacteristics of the aluminum material, and this is efficient toreduce the inertia loss of the rotor frame while achieving animprovement in processability. In conclusion, by integrally forming therotor frame with the rotor by use of the aluminum material, moreparticularly, an aluminum alloy, etc., the manufacture of the rotor canbe simplified considerably. Also, when it is desired to perform anadditional process on the rotor frame for the sake of a more accuratestructure, the processing of the rotor can be accomplished easily byvirtue of its improved processability.

Meanwhile, by the coupling holes 137 for the coupling of the connector16 and the positioning holes 138 for the determination of the assemblingposition of the connector 16, which are formed around the through-hole131 in the hub 132 of the rotor frame, the connector 16, which will beserration-coupled to the outer circumference of the rear end of theshaft 4 at a position behind the rear bearing 6 b, can be easilyassembled to the rotor 13.

Specifically, once the positioning protrusions 160 of the connector 16are inserted into and engaged in the positioning holes 138 of the rotor13, the coupling holes 137 of the rotor 13 are automatically alignedwith the coupling holes 162 of the connector 16, thus allowing thecoupling members 15 b to be coupled through the coupling holes 137 and162 of the rotor 13 and the connector 16. As a result, the connector 16can be easily assembled with the rotor 13.

In this case, the connector 16 is injection molded by use of a resinmaterial and has a different vibration mode from the aluminum rotor 13.Accordingly, the connector 16 serves to allow the vibration of the rotor13 to be transmitted to the shaft 4 in an alleviated state. Here, it isnoted that the connector 16 may be integrally formed with the rotorframe via insert molding.

The connector 16 is formed with the serration 164 at the innercircumference of the hub 163. Accordingly, as the serration 164 areengaged with the serration 400 formed at the rear end of the shaft 4,the rotating force of the rotor 13 can be directly transmitted to theshaft 4 through the connector 16.

The connector 16 is also formed at the outer circumference of the hub163 with the reinforcing ribs 601 to reinforce the strength of the hub163.

Hereinafter, a drum type washing machine according to a secondembodiment of the present invention will be described in detail withreference to FIGS. 8 to 13. The present embodiment has approximately thesame configuration as that of the above described first embodimentexcept for a structure for coupling fixedly the motor to the rear wallportion of the tub. Accordingly, the description of the sameconfiguration as the above described embodiment will be omitted.

FIG. 8 is a longitudinal sectional view schematically illustrating theconfiguration of a drum type washing machine using a direct connectionmotor according to the present embodiment, and FIG. 9 is an enlargedlongitudinal sectional view of the portion “A” of FIG. 8, illustratingthe configuration of a drive unit included in the drum type washingmachine according to the second embodiment of the present invention.

FIG. 10 is a perspective view illustrating the rear wall portion of thetub shown in FIG. 9, FIG. 11 is a top perspective view of the bearinghousing shown in FIG. 9, FIG. 12 is a rear perspective view of thebearing housing, and FIG. 13 is a sectional view taken along the lineI-I of FIG. 11.

The present embodiment has a feature in that a bearing housing 7′ isintegrally formed with the tub 2, which is made of a plastic material,at the center of the rear wall portion of the tub 2. The bearing housing7′ of the present embodiment can rotatably support the shaft 4 whileallowing a stator 6 to be coupled fixedly to the rear wall portion ofthe tub 2 therethrough.

Here, the bearing housing 7′ is made of an aluminum alloy, etc. In thepresent embodiment, the bearing housing 7′ is inserted into the rearwall portion of the tub 2 while the plastic tub 2 is injection molded,so as to be integrally formed with the rear wall portion of the tub 2.

Referring to FIG. 9, the bearing housing 7′ includes a bearingsupporting portion 7 a for supporting bearings, the bearing supportingportion 7 a having a sleeve form, and a stator coupling portion 7 bintegrally formed with the bearing supporting portion 7 a to be extendedradially from a rear end of the bearing supporting portion 7 a. Thestator coupling portion 7 b is inserted into the rear wall portion ofthe tub 2 so that only stator coupling holes 700 b formed in the statorcoupling portion 7 b are exposed to the outside.

Referring to FIGS. 11 and 12, the stator coupling portion 7 b of thebearing housing 7′ is extended radially and outwardly from the bearingsupporting portion 7 a in the form of a sleeve, and has stepped regions70 b-1, each of the stepped portions 70 b-1 being stepped at least onetime in a radial outward direction thereof.

The stator coupling portion 7 b of the bearing housing 7′ further hasplane regions 70 b-2 defined between the respective adjacent steppedregions 70 b-1.

The bearing housing 7′ of the present embodiment has a feature in thatthe stepped regions 70 b-1 and the plane regions 70 b-2 of the statorcoupling portion 7 b are continuously arranged to be connected to eachother.

That is to say, the stator coupling portion 7 b of the bearing housing7′ consists of the stepped regions 70 b-1 configured to be stepped in aradial outward direction thereof and the plane regions 70 b-2 configuredto define planes between the respective adjacent stepped regions 70 b-1.Here, of the regions of the stator coupling portion 7 b, the regions 70b-1 are extended in a radial outward direction from the upper end of thebearing supporting portion 7 a so that they are stepped downward per apredetermined distance in the radial outward direction. Also, of theregions of the stator coupling portion 7 b, the regions 70 b-2 areconnected to a front end of the bearing housing 7′ and have a planestructure.

The bearing housing 7′ is formed, around a rear end thereof, with aresin filling groove 750 a, for the sake of improving a coupling forcewith the tub 2 during insert injection molding.

Referring to FIGS. 10 and 11, the stator coupling portion 7 b haspositioning recesses 710 b formed near some of the stator coupling holes700 b at positions corresponding to positioning protrusions formed atthe stator 6.

As shown in FIG. 10, the rear wall portion of the tub 2 is formed with aplurality of protruding bosses 210 at positions corresponding tospecific positions near the stator coupling holes 700 b of the statorcoupling portion 7 b included in the bearing housing 7′. The protrudingbosses 210 serve to prevent the stator 6 from coming into direct contactwith the stator coupling portion 7 b, in order to prevent an insulatorof the stator 6 from being damaged by a coupling force applied in thecourse of coupling the stator 6.

Preferably, the stator coupling portion 7 b is formed with a rib 720 bin a circumferential direction at a position spaced apart from thecenter of the bearing supporting portion 7 a by a predetermineddistance, for the sake of increasing a coupling force with a resinmaterial upon injection molding of the tub 2. Although it is preferablethat coupling bosses 70 b, each having the stator coupling hole 700 b,are arranged along the rib 720 b, it is not essential to form thecoupling holes 700 b along the rib 720 b.

In addition, the rear wall portion of the tub 2 is formed withcircumferential and radial reinforcing ribs 201 except for a regioncorresponding to the stepped regions of the bearing housing 7′, for thesake of reinforcing the strength of the rear wall portion of the tub 2.

Alternatively, differently from the above described configuration of thestator coupling portion 7 b of the bearing housing 7′, although thestator coupling portion 7 b of the bearing housing 7′ is extended in aradial outward direction from the bearing supporting portion 7 a in theform of a sleeve, it is branched into a plurality of portions spacedapart from one another by a regular distance in a circumferentialdirection, to obtain a radially distributed structure.

In the present embodiment, as a result of providing the bearing housing7′ with the coupling bosses 70 b having the stator coupling holes 700 b,it is unnecessary to perforate coupling holes in the tub 2.

Specifically, according to the above described configuration of thepresent embodiment, the stator 6 is secured to the rear wall portion ofthe tub 2 as it is bolted to the stator coupling holes 700 b of thecoupling bosses 70 b provided at the stator coupling portion 7 b of thebearing housing 7′ that was previously embedded in the rear wall portionof the tub 2.

Near some of the coupling holes 700 b of the stator coupling portion 7 bare formed the positioning recesses 710 b corresponding to thepositioning protrusions formed at the insulator of the stator 6. Withthe provision of the positioning means, the stator 6 can be coupled tothe rear wall portion of the tub 2 with an improved workability.

Preferably, the positioning recesses 710 b, which are formed at thestator coupling portion 7 b of the bearing housing 7′, is configured sothat it is exposed to the outside rather than being covered with a resinmaterial. Conversely, if the positioning recesses are formed at theinsulator of the stator 6, the stator coupling portion 7 b of thebearing housing 7′ may be formed with the positioning protrusions.

Hereinafter, a drum type washing machine according to a third embodimentof the present invention will be described in detail. Similarly, thedescription of the same configuration as that of the above describedfirst and second embodiments will be omitted.

FIG. 14 is a sectional view illustrating a drive unit of a drum typewashing machine according to the present embodiment.

The present embodiment has a feature in that a supporter is interposedbetween the rear wall portion of the tub and the stator. Here, thesupporter serves not only to reinforce the rigidity of the rear wallportion of the tub, but also to allow the stator to be more stronglysecured to the rear wall portion of the tub.

Accordingly, the washing machine according to the present embodimentcomprises the tub 2 installed in the cabinet (not shown) and used toreceive wash water therein, the drum 3 rotatably provided in the tub 2and adapted to wash laundry received therein as it is rotated, the shaft4 penetrated through the tub 2 and connected to the drum 3, the shaft 4being adapted to transmit the drive force of the motor 5 to the drum 3,the stator 14 having the winding portions around which the coils arewound, the stator 14 being coupled fixedly to the rear wall portion ofthe tub 2, and the supporter interposed between the rear wall portion ofthe tub 2 and the stator 14 and adapted to increase the couplingstrength between the tub 2 and the stator 14.

In the present embodiment, the metallic bearing housing 8 may beintegrally formed with the rear wall surface 200 of the tub 2 via insertmolding, simultaneously with the injection molding of the plastic tub 2.

Now, the supporter 27 of the present embodiment will be described inmore detail.

The supporter 27 is interposed between the rear wall portion of the tub2 and the stator 14, more particularly, between the rear wall surface200 of the tub 2 and the stator 14. The supporter 27 has approximatelythe same outer contour as that of the rear wall surface 200 of the tub 2and is secured to the rear wall surface 200 of the tub 2 when the stator14 is coupled to the tub 2. Thereby, the supporter 27 serves to supportthe stator 14 while maintaining the stator 14 coaxially with the tub 2.

The supporter 27 has a front end coming into close contact with an innersurface of a rib 203 that is provided at a side of the rear wall surface200 of the tub 2. A rear end of the supporter 27 is configured to comeinto close contact with an outer circumference of the rear end of thebearing housing 7′, which is exposed to the outside without beingsurrounded by the hub 132 of the rotor frame provided at the center ofthe rear wall surface 200 of the tub 2.

Now, a drum type washing machine according to a fourth embodiment of thepresent invention will be described in detail with reference to FIG. 15.

The present embodiment has a feature in that a distance regulationwasher is provided in addition to the configuration of the abovedescribed fourth embodiment. The distance regulation washer isinterposed between the supporter and the stator and adapted to regulatea distance between the tub and the stator.

More specifically, in the present embodiment, the distance regulationwasher 500 may be interposed between the supporter 27 and the stator 14coupled to the supporter 27 and adapted to regulate a distance betweenthe tub 2 and the stator 14. Preferably, the distance regulation washer500 has an annular form suitable to stably separate the stator 14 fromthe tub 2. The distance regulation washer 500 may be formed, in acircumferential direction thereof, with a plurality of coupling holes.Accordingly, the distance regulation washer 500 performs the function ofallowing the stator 14 to be coupled to the tub 2 with a predetermineddistance therebetween.

Generally, the size of the tub and consequently, the capacity of themotor may be changed according to diversified capacities of washingmachines. Also, the capacity of the motor is mainly determined by themagnitude of current applied to the motor. Accordingly, it can be saidthat the stator is the most important factor of determining the capacityof the motor. Although it is preferable to standardize the size of therotor in views of price saving for the sake of mass production, this hasan essential necessity for guaranteeing the flexible coupling of themotor even if the size of the stator is changed.

For this reason, if a small size stator is used, the distance regulationwasher 500 has to be used to prevent the rotor from coming into contactwith the rear wall portion of the tub when the stator is coupled withthe rotor.

It will be apparent to those skilled in the art that variousmodifications and variations, related to the size, shape, and materialof the constituent elements, can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A washing machine comprising: a tub for receiving wash water therein;a drum rotatably disposed in the tub and adapted to wash laundryreceived therein; a shaft penetrated through the tub to thereby beconnected to the drum, the shaft being adapted to transmit a drive forceof a motor to the drum; a stator coupled fixedly to a rear wall portionof the tub; and a rotor including at least one magnet, a back yokedefining a magnetic path, and a rotor frame rotatably disposed at theoutside of the stator, the rotor frame being connected to the shaft soas to transmit a rotating force of the rotor to the shaft, wherein therotor frame comprises a side wall portion and a rear wall portion, andis made of an aluminum material.
 2. The washing machine according toclaim 1, wherein the rotor frame is formed by die casting, and the sidewall portion and the rear wall portion of the rotor frame are integrallyformed with each other.
 3. The washing machine according to claim 2,wherein the rear wall portion of the rotor frame is provided, at acenter position thereof, with a connector, which is serration-coupledonto an outer circumference of the shaft and adapted to transmit therotating force of the rotor to the shaft.
 4. The washing machineaccording to claim 3, wherein the connector is made of an insulatingmaterial and integrally formed with the rotor frame by insert molding.5. The washing machine according to claim 2, further comprising: abearing housing provided between the rear wall portion of the tub andthe stator and coupled fixedly to both the tub and the stator, thebearing housing receiving at least one bearing therein to rotatablysupport the shaft.
 6. The washing machine according to claim 5, whereinthe bearing housing is made of a metallic material.
 7. The washingmachine according to claim 2, wherein the side wall portion of the rotorframe is extended forward from an edge of the rear wall portion, and theside wall portion of the rotor frame is formed, in a circumferentialdirection thereof, with a ledge having a seating plane for supportingthe magnet thereon.
 8. The washing machine according to claim 2, whereinthe stator comprises: a stator core including a winding portion aroundwhich a coil is wound and an annular body portion defining the magneticpath; and an insulator for insulating the stator core from the coil. 9.The washing machine according to claim 2, wherein the stator has thirtysix poles, and the rotor has forty eight poles.
 10. The washing machineaccording to claim 2, wherein the back yoke is attached to an innersurface of the side wall portion of the rotor frame in a circumferentialdirection by use of an adhesive, and the magnet is attached to an innersurface of the back yoke in a circumferential direction by use of anadhesive.